Traditionally, motion control devices for marine vessels, such as fin roll stabilizers, have been powered hydraulically. In this application, hydraulics offer distinct advantages over other methods of providing power, such as electric motors. For instance, hydraulic actuators, or cylinders, can deliver a tremendous amount of force in a relatively small package, with little to no backlash or physical wear.
The drawbacks of traditional hydraulic systems are numerous. First, traditional hydraulic systems require numerous components and large plumbing systems spread out about the vessel, especially when multiple fin stabilizers are used. These systems must be fitted to the engine or generator's power take off, or to separate electric motors. A reservoir must be installed to supply the hydraulic pumps with fluid. The fluid must be clean and kept from overheating, so filters and a cooling system must be installed. An intricate network of hoses and pipes must be maintained to keep hydraulic fluid flowing to and from each and every hydraulic system component and consumer. With so many components, these systems can be costly to acquire and install, and need to be continually and carefully maintained.
The alternative to traditional hydraulic systems has been the use of electric motors to rotate the fins either directly or through a reduction gear. Direct drive motors are necessarily rather large due to the high torque requirements of a fin stabilizer. Adding a reduction gear between the motor and the fin can reduce the size requirement of the motor, but at the expense of the gear arrangement being subject to wear and backlash. In either case, the motors would be at risk of overheating and would require a cooling system.